package com.atguigu.common.utils;

import java.text.DecimalFormat;
import java.util.*;

/**
 * 生成4位和6位随机数字
 */
public class RandomUtils {
    private static final Random random=new Random();
    private static final DecimalFormat fourdf=new DecimalFormat("0000");
    private static final DecimalFormat sixdf=new DecimalFormat("000000");

    public static String getFourBitRandom(){
        return fourdf.format(random.nextInt(10000));
    }
    public static String getSixBitRandom(){
        return sixdf.format(random.nextInt(1000000));
    }

    /**
     * 给定数组，抽取n个数据
     * @param list
     * @param n
     * @return
     */
    public static ArrayList getRandom(List list,int n){
        Random random = new Random();
        HashMap<Object, Object> hashMap = new HashMap<>();
        //生成随机数字并存入HashMap
        for (int i = 0; i < list.size(); i++) {
            int number = random.nextInt(100) + 1;
            hashMap.put(number,i);
        }
        //从HashMap导入数组
        Object[] robjs = hashMap.values().toArray();
        ArrayList r = new ArrayList();
        //遍历数组并打印数据
        for (int i = 0; i < n; i++) {
            r.add(list.get((int)robjs[i]));
            System.out.println(list.get((int)robjs[i])+"\t");
        }
        System.out.println("\n");
        return r;
    }
}
